The invention is based on a priority patent application EP 07121384.7 which is hereby incorporated by reference.
This invention relates generally to vision systems for vehicles and, more particularly, to rear-view vision systems which provide the vehicle operator with scenic information in the direction rearward of the vehicle. More particularly, the invention relates to a rear-view vision system utilizing image capture devices, such as CMOS imaging arrays in external rear view mirrors to support lane change in a driver assistant system.
A long-felt need in the art of vehicle rear-view vision systems has been to eliminate or at least minimize exterior rear-view mirrors by utilizing image capture devices, such as cameras, in combination with displays. This would be beneficial because it would reduce wind drag on the vehicle, wind noise and vehicle weight and so in conclusion the C02 emission of the vehicle. Furthermore, rear-view mirrors protrude a substantial distance from the side of the vehicle, which makes manoeuvring in tight spaces more difficult. Image capture devices are capable of positioning in a greater variety of locations on the vehicle, providing more flexibility of vehicle styling. It is further expected that camera systems would greatly reduce the blind spots to the sides and rear of the vehicle common with vehicles equipped with conventional rear-view mirror systems. The driver cannot perceive vehicles, objects, or other road users in such blind spots without turning his or her body, which interferes with forward-looking visual activities.
Camera-based rear-view vision systems for vehicles have not obtained commercial acceptance and are in addition not allowed as stand alone solution under different legislations. One difficulty with proposed systems has been that they present a large amount of visual information in a manner which is difficult to comprehend. This difficulty arises from many factors. In order to significantly reduce blind spots, multiple image capture devices are typically positioned at various locations on the vehicle. The image of an object behind the equipped vehicle is usually captured by more than one image capture device at a time and displayed in multiple images. This may confuse the driver as to whether more than one object is present.
A camera system provides a monocular view of the scene, compared to the binocular, or stereoscopic, view obtained when the scene is viewed through a rear-view mirror. This makes the ability to judge distances in a camera system a problem. This effect is most noticeable at distances close to the vehicle where stereoscopic imaging is relied upon extensively by the driver in judging relative locations of objects. Therefore, known camera systems fail to provide to the driver important information where that information is most needed—at small separation distances from surrounding objects.
Another difficulty with camera systems is that, in order to provide a sufficient amount of information, the camera system typically presents the driver with a greatly increased field of view. This improves performance by further reducing blind spots at the side and rear of the vehicle. However, an increased field of view is often obtained by utilizing a wide-angle lens which introduces distortion of the scene and further impairs the ability of the driver to judge distances of objects displayed. The problem with such distortion of the scene is that the driver must concentrate more on the display and take a longer time to interpret and extract the necessary information. This further distracts the driver from the primary visual task of maintaining awareness of vehicles and other objects in the vicinity of the driven vehicle.
In the U.S. Pat. No. 5,670,935 a rear vision system is disclosed which one image capture device directed rearwardly with respect to the direction of travel of the vehicle. A display system displays an image synthesized from output of the image captive device. A plurality of image capture devices my be provided and the display system displays a unitary image synthesized from outputs of the image captive devices which approximates a rearward-facing view from a single location, such as forward of the vehicle. To establish this system at least three video cameras must be mounted on the vehicle to get the overlaps of view necessary and to avoid blind spot areas. In this patent the information is displayed on a screen again, which makes it obligatory for the driver to adjust eyes between wide and narrow.
Another disclosure US 2006 0250224 describes a solution in which the overview of the near environment of the vehicle is not presented by a video display but by a warning light. The warning light is actuated by a video controlled camera system wherein a first video sensor is located in a rear view mirror and second sensor in the warning light. The warning light is actuated by a video controlled camera system wherein a first video sensor is located in a rear view mirror and second sensor in the rear light of the vehicle. Here the blind spot detection of one side of the vehicle is realized with two video sensors looking along the lanes rearwardly.
The JP 2003118487 discloses two sensors which are used to record video images for a recording system and for a full image display. The sensors are wide angle sensors that can have an inclination versus the vehicle. The system is not used to reduce blind spot and for a lane change assistant.Many blind spot detection systems are known using several cameras placed at different positions of the vehicle. The use of several cameras in a vehicle makes it necessary to connect the cameras to a communication system, a bus system and to bring electrical connection to the different camera positions in the vehicle. This is an additional effort and additional cost for the manufacturing of the security system.